In the flat panel display technology, an OLED (organic light emitting diode) display has the advantages of lightness and thinness, low-power consumption, high contrast, high color gamut, and capability of achieving flexible display, etc. The OLED display is a developing trend of displays in a next generation. The OLED display includes two approaches including PMOLED (passive mechanical and electrical excitation organic light emitting diode) and AMOLED (active matrix organic light emitting diode), where the AMOLED display approach can be achieved by a structure of combining a LTPS (low temperature polycrystalline silicon) backboard with a FMM Mask (fine metal mask), and it is suitable for a large size panel. For example, a structure manner of combining the LTPS backboard with the FMM Mask can be suitable for the application of the large size panel such as a monitor and a television, etc. At present, the manner of combining the LTPS backboard with the FMM Mask is preliminarily matured, and has achieved mass production.